From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id E18D12459E5 for ; Wed, 27 May 2026 14:12:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779891146; cv=none; b=BskllD9dcsnGfi0EHxN2tDe67SulLDC7w7jCLuUFeBc7Pjtbc4MDkSkjKsftK1v+J6VVTDMh4i/AMAnyemy+rVj3Bh1DjmkQOiUdHjRuzkBKacwjUEX8K7NmMSnadxynMS0av4QN98w2ygK2Qz4cf5n6hSuFtMa8A7UFOjpqqZE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779891146; c=relaxed/simple; bh=u3OCxUvtZcz8HMh6U6iOvnXk3mPDlsgfuMXPwG1nTnM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=MADCeUL2UqLa3gNfXR7xSawf24OdiJG1ZVUaoDNB/bEFG3ItPnhDJTLzY28Ub7Ophsl4a6j9ZnoidLaOvXu8kB9peZTS1EVp2e9mXzN6nzlfbPU2Kl0zn5l3xZwFLhLb1gXClECKFLLjB+sJuHZEhTPsjdi5d46fjCnuD3NnYrQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=MKSa8BSt; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="MKSa8BSt" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 3E0D927DC; Wed, 27 May 2026 07:12:19 -0700 (PDT) Received: from [10.1.36.149] (XHFQ2J9959.cambridge.arm.com [10.1.36.149]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 714813F905; Wed, 27 May 2026 07:12:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1779891144; bh=u3OCxUvtZcz8HMh6U6iOvnXk3mPDlsgfuMXPwG1nTnM=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=MKSa8BSt9BSP9qCifI6PxRc6JlT2Rvcm3UBj7hlH3DOwlOqZ9GbA9MJXvTzduITUK cN/VxqCg7WM5rVROAvZB87oajUO9GN3RvAL+HjURwBq+pFlLCnauo53bTJRALtYeAF CU7fyXOpRpolf4zP8xtVI/2LDMhBuehQgWhWCh8s= Message-ID: Date: Wed, 27 May 2026 15:12:20 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC V2 08/14] arm64/mm: Route all pgtable writes via pxxval_set() Content-Language: en-GB To: Anshuman Khandual , linux-arm-kernel@lists.infradead.org Cc: Catalin Marinas , Will Deacon , Mark Rutland , Lorenzo Stoakes , Andrew Morton , David Hildenbrand , Mike Rapoport , Linu Cherian , Usama Arif , linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20260513044547.4128549-1-anshuman.khandual@arm.com> <20260513044547.4128549-9-anshuman.khandual@arm.com> From: Ryan Roberts In-Reply-To: <20260513044547.4128549-9-anshuman.khandual@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 13/05/2026 05:45, Anshuman Khandual wrote: > Currently pxxval_set() is defined as WRITE_ONCE() but this will change for > D128 pgtable builds, for which WRITE_ONCE() is not sufficient for single > copy atomicity. > > In future this infrastructure can be used for D128 to maintain single copy > atomicity semantics with inline asm blocks. > > Cc: Catalin Marinas > Cc: Will Deacon > Cc: Ryan Roberts > Cc: Mark Rutland > Cc: linux-arm-kernel@lists.infradead.org > Cc: linux-kernel@vger.kernel.org > Signed-off-by: Anshuman Khandual > --- > Changes in RFC V2: > > - Renamed all ptdesc_ instances as pxxval_ instead > > arch/arm64/include/asm/pgtable.h | 11 ++++++----- > arch/arm64/mm/mmu.c | 4 ++-- > 2 files changed, 8 insertions(+), 7 deletions(-) > > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h > index 72da582e8d12..c71bb829e9f1 100644 > --- a/arch/arm64/include/asm/pgtable.h > +++ b/arch/arm64/include/asm/pgtable.h > @@ -85,6 +85,7 @@ static inline void arch_leave_lazy_mmu_mode(void) > } > > #define pxxval_get(x) READ_ONCE(x) > +#define pxxval_set(x, val) WRITE_ONCE(x, val) Same comment as for pxxval_get(): I think it would be clearer if this was an inline function that took a pointer. Thanks, Ryan > > #define pmdp_get pmdp_get > static inline pmd_t pmdp_get(pmd_t *pmdp) > @@ -385,7 +386,7 @@ static inline pte_t pte_clear_uffd_wp(pte_t pte) > > static inline void __set_pte_nosync(pte_t *ptep, pte_t pte) > { > - WRITE_ONCE(*ptep, pte); > + pxxval_set(*ptep, pte); > } > > static inline void __set_pte_complete(pte_t pte) > @@ -856,7 +857,7 @@ static inline void set_pmd(pmd_t *pmdp, pmd_t pmd) > } > #endif /* __PAGETABLE_PMD_FOLDED */ > > - WRITE_ONCE(*pmdp, pmd); > + pxxval_set(*pmdp, pmd); > > if (pmd_valid(pmd)) > queue_pte_barriers(); > @@ -921,7 +922,7 @@ static inline void set_pud(pud_t *pudp, pud_t pud) > return; > } > > - WRITE_ONCE(*pudp, pud); > + pxxval_set(*pudp, pud); > > if (pud_valid(pud)) > queue_pte_barriers(); > @@ -1003,7 +1004,7 @@ static inline void set_p4d(p4d_t *p4dp, p4d_t p4d) > return; > } > > - WRITE_ONCE(*p4dp, p4d); > + pxxval_set(*p4dp, p4d); > queue_pte_barriers(); > } > > @@ -1131,7 +1132,7 @@ static inline void set_pgd(pgd_t *pgdp, pgd_t pgd) > return; > } > > - WRITE_ONCE(*pgdp, pgd); > + pxxval_set(*pgdp, pgd); > queue_pte_barriers(); > } > > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index 7fbb2ef86cfa..6eb92d8f46be 100644 > --- a/arch/arm64/mm/mmu.c > +++ b/arch/arm64/mm/mmu.c > @@ -76,7 +76,7 @@ void noinstr set_swapper_pgd(pgd_t *pgdp, pgd_t pgd) > * writable in the kernel mapping. > */ > if (rodata_is_rw) { > - WRITE_ONCE(*pgdp, pgd); > + pxxval_set(*pgdp, pgd); > dsb(ishst); > isb(); > return; > @@ -84,7 +84,7 @@ void noinstr set_swapper_pgd(pgd_t *pgdp, pgd_t pgd) > > spin_lock(&swapper_pgdir_lock); > fixmap_pgdp = pgd_set_fixmap(__pa_symbol(pgdp)); > - WRITE_ONCE(*fixmap_pgdp, pgd); > + pxxval_set(*fixmap_pgdp, pgd); > /* > * We need dsb(ishst) here to ensure the page-table-walker sees > * our new entry before set_p?d() returns. The fixmap's